This invention relates generally to the testing of electronics circuitry, and more particularly concerns wiring terminals adapted for use with spring probe assemblies associated with terminal boards. The invention provides all of the highly desired features of high density, low profile packaging, without the inherent high cost, extended delivery and reliability problems found with existing interconnection alternatives.
Such known interconnection alternatives include: (a) multi-layered boards characterized by plate-through holes in multilayers; (b) "wire-wrap" boards, wherein wires are forcibly wrapped several times about polygonal cross-section terminal pins; and (c) "stitch-weld" connections.
(a) The design/manufacturing cycle of multilayer boards is typically several weeks or months due to the sequential task in fabrication. Probably the biggest disadvantage of multilayers is the difficulty, cost and delay in effecting engineering change orders. External wiring is commonly used where wire termination provisions are practically nonexistent. Existing circuits are "erased" with a sharp knife and the result, in general, is nonacceptable. Another disadvantage is inconsistancy in fabrication. At best, the production of plated-through-holes in multilayers is a highly controlled process with the final reliability directly dependent on several different steps being successfully completed. Yield rates of 70% (30% have defects) is not uncommon on large, high density boards with 8 to 10 layers. This manufacturing problem is compounded by the fact that the defects are internal to the board and cannot be detected by means of visual inspection. As a result, the manufacturer or user has a choice of one of two very expensive alternatives: PA1 I Use special electronic test equipment for prescreening the boards prior to adding value (components and labor) PA1 Ii Adding value and detecting the failures at board or system test. PA1 (b) In the production of wire wrap boards, it is necessary to remove the top (Z) level wires in order to delete or remove a wire on bottom level. Since the wire cannot be rewrapped, all wires must be replaced. As can be seen, a simple interconnect change can require removal and replacement of several wires. Also, wire wrap techniques require that the wire be cut and wrapped at each terminal. This creates a serially connected circuit with two wraps at each terminal in a circuit string; furthermore wire wrapped connections are not easily soldered. In addition if a pin is to be connected to an adjacent pin 0.100 inch away, a minimum wire length of 11/2 inches must be used. Due to the high profile of wire wrap boards, the wires are usually channeled between the pins in a prescribed pattern causing many parallel runs. Such construction limits its usage except at comparatively low frequencies. PA1 (c) A large disadvantage with "stickweld" techniques is the requirement that stainless steel is required to effect a termination. Typically, a special nickel alloy wire is required, at cost many times greater than ordinary commercial grade wiring, such as copper or aluminum wire. Also, with stickweld, extreme care must be taken when applying the break-thru pressure of the wire insulation, as well as electrical pulse, and energy levels. The quality of the termination with stickweld is directly dependent on several variables. A weld schedule must be established with the proper watt-second setting of the power supply for each type of terminal used. The watt-second setting will vary according to the geometry of the terminal or the type stainless steel used in the terminal or wire size, insulation type and conductor material used. Watt-second settings range from 2 to 20 watt-seconds. Quality procedures must be established to detect blown welds, cracks, expulsion, inclusions, open welds, pitting, spitting, voids, etc., on all terminations. PA1 (a) providing multiple metallic terminals on the board, such terminals having slots with open mouths between terminal edges, PA1 (b) providing wiring with insulation thereon, and PA1 (c) forcibly displacing the wiring sidewardly into the slots via their mouths in such manner that the insulation is sheared off the wire by the terminal edges, and the wiring is locally deformed as it enters the slots thereby to produce metal-to-metal contact between the wiring and the terminal metal at the inner sides of the slots. PA1 (a) a terminal board, PA1 (b) multiple metallic terminals projecting from the board, PA1 (c) such terminals having slots extending generally axially therein from open terminal end mouths having edges, and PA1 (d) wiring forcibly displaced sidewardly past the edges and into the slots via said mouths, the axes of the wiring extending generally normal to the axes of the terminals, and opposite sides of the wiring having metal-to-metal contact with the inner walls of said terminals spaced at opposite sides of the slots, the wiring projecting through the slots and extending between different terminals. PA1 (a) Board fabrication is directly dependent upon the mechanical dimensions of a slotted terminal and wire diameter, both of which are exactly controlled in their manufacture. Terminations can be visually inspected and the board is easily repaired. Cost savings are especially pronounced with lower production quantities of boards, as compared with multi-layer boards referred to above. PA1 (b) Slant or planar packaging density is considerably improved over prior methods. Due to the lower profile of wire terminals, it is possible to have two or three terminal boards in the same space as one wire wrap type board. PA1 (c) Wiring changes are more easily made on boards as described. Since multiple wires can be stacked in a slot, wires or circuits can be deleted by simply snipping wires, and new circuits can be added with equal ease by staking new wires. PA1 (d) Ordinary wire may be used, as compared with expensive stainless steel wire require for stickweld connections. PA1 (e) Terminals are easily and economically soldered, if required, such that the mechanical connection and solder offer a comparable or better connection than the soldered component to which it interconnects.
Since the boards are nonrepairable, those with internal shorts or opens are usually discarded (with components), at great expense.